How do the various measures taken around the world for Covid-19 compare with pre-pandemic guidelines, presumably based on decades of research and experience?

These are the 2019 WHO guidelines on Non Pharmaceutical Interventions (NPIs) for influenza pandemics: link. Table-1 in page-9 (reproduced below) is the summary.

Specifically, look at the last row. Not recommended in any circumstances includes: contact tracing, quarantine of exposed individuals, entry and exit screening, border closure. Forget wring-the-neck-of-the-poor lockdowns, even "quarantine of exposed individuals" is in the "not recommended in any circumstances" category.

Surely, the WHO had the following pandemics in mind, while writing these guidelines:

  • 1918 Spanish flu (DPM 100-200 times that of current Covid DPM),
  • 1957-58 Asian flu (DPM 4-5 times that of current Covid DPM),
  • 1968-69 Hong Kong flu (DPM 1.8 times that of current Covid DPM)

Note: even flu has asymptomatics, and asymptomatics can shed the flu virus: "Most healthy adults may be able to infect others beginning 1 day before symptoms develop...", " may be able to pass on the flu to someone else before you know you are sick...", "Some people can be infected with the flu virus but have no symptoms. During this time, those people may still spread the virus to others."

As per Sweden's response, Covid-19 would fall in the "Moderate" category in the table; may have been originally thought to be in the "High" category.